Conventionally, a disc cartridge accommodating a disk recording medium such as an optical disc on which a data signal is recorded comprises a cartridge body formed by placing together and connecting a pair of upper and lower halves formed by shaping a plastic material such as an ABS resin and by accommodating the disk recording medium in this cartridge body so that it can rotate. The disc cartridge is mounted in a recording and/or reproducing apparatus in a state with the disk recording medium accommodated therein as it is. The disk recording medium accommodated in the cartridge body is chacked on a disc table constituting part of the disc rotating mechanism with a center portion arranged on the recording and/or reproducing apparatus side and is operated to rotate together with the disc table.
In a disc cartridge using an optical disc as the disk recording medium, when the optical disc accommodated in the cartridge body is chacked on the disc table and rotated together with the disc table, the signal recording portion formed on the main surface is scanned by a light beam emitted from an optical pick-up so as to reproduce the recorded data signal.
Further, when recording a data signal, an external magnetic field subjected to magnetic field modulation in accordance with the data signal to be recorded from a magnetic head serving as an external magnetic field generation means is applied to this signal recording portion in a state where the light beam emitted from the optical pick-up is irradiated to the signal recording portion of the optical disc so as to record a predetermined data signal.
The optical disc accommodated in the disc cartridge generally comprises a disc substrate formed by shaping a transparent plastic material and a hub for magnetic clamping which is formed by a magnetic plate such as a metal plate and installed in a center hole provided at the center portion of this disc substrate. On the main surface of this disc is provided a signal recording portion on which recording tracks in which the data signal is recorded are formed in concentric circles around the center hole.
In the lower half of the cartridge body is provided a central opening which is positioned at the center and into which a circular disc table constituting part of the disc rotating mechanism intrudes is inserted. This central opening specifically makes the hub for the magnet clamping attached to the disc substrate so as to cover the center hole face outward.
Further, in the upper half and lower half of the cartridge body, openings for recording and/or reproduction which make one part of a data signal recording portion provided on the main surface of the optical disc face outward over the inner and outer circumferences and to which recording and reproduction means such as an optical pick-up or an external magnetic field generation means arranged on the recording and/or reproducing apparatus side face are provided at facing positions. These openings for recording and/or reproduction are positioned at the center of the cartridge body in the horizontal direction and are as rectangular openings covering an area from the front side to a position close to the central opening. Note that, in a disc cartridge accommodating an optical disc used only for reproduction, only an opening for reproduction is formed in the lower half side—the upper half side is closed.
Further, the disc cartridge has movably attached to it a shutter member for closing the opening for recording and/or reproduction to prevent the intrusion of the dust etc. into the cartridge body and, at the same time, for preventing damage to the optical disc accommodated in the cartridge body in a state when the cartridge is not loaded in the recording and/or reproducing apparatus. This shutter member is moved from the position closing the opening for recording and/or reproduction to the opening position by a shutter opening member provided on the recording and/or reproducing apparatus side by the operation of loading the disc cartridge in the recording and/or reproducing apparatus. Further, when the disc cartridge is loaded in the recording and/or reproducing apparatus, the disc cartridge bull enters via the central opening and the optical disc accommodated in the cartridge body is chacked on this disc table.
Note that the upper half and lower half of the cartridge body are formed as generally shallow dish rectangular shapes with rising circumferential walls constituting the circumferential side wall of the cartridge body integrally formed along the circumferential edges. Further, on the inner surfaces at which the upper and lower halves face each other, annular walls for forming the portion accommodating the recording medium which are mated with each other to form the disc accommodating portion are formed so as to be inscribed in the rising circumferential walls. At the same time, mating projections which constitute a plurality of fusing portions which are to be mated with each other and joined are provided. These mating projections are arranged at appropriate positions of the inner surfaces at which the upper half and lower half face each other so that no gap will be produced between the upper half and lower half when the upper half and the lower half are mated and joined and so that therefore no dust etc. will intrude into the inside.
Here, explaining the mating projections provided so as to join the upper and lower halves by fusing, these mating projections 101 and 103 are provided on the surfaces at which the upper half 100 and the lower half 102 to be mated and joined to each other and constituting the cartridge body face each other as shown in FIG. 1 and FIG. 2. These mating projections 101 and 103 are formed in a cylindrical shape. A projection 105 for the fusing of a thickness which becomes narrower toward the front end is integrally formed on an end surface 104 of the mating projection 103, provided in the lower half 102, to which an end surface 106 of the mating projection 101 provided on the upper half 100 faces. This projection 105 is formed in the shape of a ring over the entire circumference of the end surface 106 of the mating projection 101.
Note that the mating projections 101 and 103 are provided in a region surrounded by the rising circumferential walls provided on the upper and lower halves 100 and 102 constituting the circumferential walls of the cartridge body and annular walls forming the portion accommodating the recording medium constituting the disc accommodating portion.
The mating projections 101 and 103 are fused together by melting the projections 105 by application of an ultrasonic wave to the end surfaces 104 and 106 which are mated with each other in a state where the upper half 100 and the lower half 102 are connected with each other. Namely, by fusing the mating projections 101 and 103, the upper and lower halves 100 and 102 are joined with each other to constitute the cartridge body.
Note that in the ultrasonic welding method, when an ultrasonic welding device is driven in a state where the phone for generating the ultrasonic wave of the ultrasonic welding device is pressed against the main surface of either of the upper half 100 or the lower half 102 acting as the body to be fused and the ultrasonic wave is applied to the upper and lower halves 100 and 102 via the phone, the ultrasonic wave concentrates at the mated portion, that is, between the end surface 106 of the mating projection 101 provided on the upper half 100 side and the projection 105 formed on the end surface 104 of the mating projection 103 provided on the lower half 102 side so ultrasonic vibration is generated in this mated portion. The mated portion is heated due to this ultrasonic vibration, whereby the projection 105 is melted to fuse the end surfaces 106 and 104 of the mating projections 101 and 103.
In a disc cartridge connecting the upper and lower halves 100 and 102 by using the ultrasonic welding method as mentioned above, a plurality of mating projections 101 and 103 are provided on the upper and lower halves 100 and 102 and these mating projections 101 and 103 are simultaneously fused together. Further, the projection 105 for the fusing formed on the mating projection 103 on the lower half 102 side fused by the application of the ultrasonic wave is formed as a ring covering the entire circumference of the end surface 104 of the mating projection 103. For this reason, there is a case where it becomes difficult to uniformly fuse all of the plurality of sets of mating projections 101 and 103.
In order to simultaneously apply the ultrasonic wave to a plurality of sets of mating projections 101 and 103 to melt the projections105 and perform the ultrasonic welding, the time for applying the ultrasonic wave to the upper and lower halves 100 and 102 becomes long.
Further, in the disc cartridge, to prevent the staining due to the adhesion of dust etc. from being conspicuous, fine pebbling formed in the main surface on the outside of the upper and lower halves of the cartridge body. Such fine pebbling is smoothed by the contact of the phone of the ultrasonic welding device over a long time. As a result, a contact mark is formed at the portion where the phone comes into contact and the sense of beauty of the outer appearance is degraded.
Further, there also exists a concern that, due to the application of an ultrasonic wave over a long time, the optical disc will vibrate in the cartridge body, rubbing will occur between the optical disc and the walls forming the portion accommodating the recording medium constituting the disc accommodating portion, and the optical disc will be scratched or shaving powder will be generated. When the shaving powder is generated and adhers to the signal recording portion, there also exists a concern of occurrence of the omissions in the recording and/or reproduction of the data signal.
Further, in a disc cartridge accommodating a disk recording medium such as an optical disc or magnetic disc, use is made of a disc cartridge which may accommodate disk recording media of different types but having generally the same size in the cartridge body. For example, use is made of a disc cartridge accommodating an optical disc or magnetic disc having a diameter of 3.5 inch. In this type of disc cartridge, since the size of the disk-like recording media to be accommodated in the cartridge body is generally made the same, the size of the cartridge bodies is generally made the same. In this way, in a disc cartridge accommodating an optical disc or magnetic disc of a diameter of 3.5 inch, it becomes extremely difficult to distinguish the two from the outer appearance. For this reason, there also exists a concern over erroneous loading, for example, erroneously loading a disc cartridge accommodating an optical disc of a diameter of 3.5 inches or a disc cartridge accommodating a magnetic disc of a diameter of 3.5 inch in the recording and/or reproducing apparatus.
Further, in a recording and/or reproducing apparatus using a disc cartridge accommodating an optical disc as the recording medium and a recording and/or reproducing apparatus using a disc cartridge accommodating a magnetic disc as the recording medium, the recording and/or reproduction means are completely different, so if the cartridges are erroneously loaded in the apparatuses, there is a concern that not only will the recording and/or reproduction of the data signal not be carried out, but also the recording and/or reproduction means such as the optical pick-up or the magnetic head provided on the recording and/or reproducing apparatus side will be damaged.
Therefore, in the disc cartridge which accommodates disk-like recording media of different types but having generally the same size in the cartridge body, to prevent the disc cartridges from being loaded in an apparatuses other than the suitable recording and/or reproducing apparatuses, a means is provided for preventing erroneous loading. As this means for preventing erroneous loading, a means providing a recess or engagement groove in one part of the cartridge body has been known. These recess and engagement grooves for preventing erroneous loading enable the loading of only the disc cartridge suited to the recording and/or reproducing apparatus by engagement of one part of the mechanism for preventing erroneous loading provided on the recording and/or reproducing apparatus side or non-engagement of one part of the mechanism for preventing erroneous loading.
In a disc cartridge wherein the type of the disc cartridge is identified and the loading of the same to an apparatus other than the suitable recording and/or reproducing apparatus is inhibited by providing the recess or engagement groove in one part of the cartridge body in this way, there is a concern that, if the disc cartridge is erroneously loaded in the recording and/or reproducing apparatus, the cartridge body will be damaged when the mechanism for preventing erroneous loading is engaged with the recess or engagement groove with which it should not originally be engaged. Particularly, in a disc cartridge wherein the upper and lower halves are joined by ultrasonic welding, there is a concern that the upper and lower halves will come apart.